Math Problem Statement

A process in continuous time X(t) takes either the value 1 or 2. Solve the given queries related to the Markov process and the corresponding probabilities.

Solution

To solve the questions provided in the image, I'll break down the parts systematically:


Question 1: Transition Matrix and p11(t)p_{11}(t)

The process is a continuous-time Markov process with two states (11 and 22). The transition probabilities are defined as:

\begin{cases} h & \text{if } j \neq k, \\ 1-h & \text{if } j = k. \end{cases}$$ #### (a) Transition Probability Matrix $$P(t)$$: Using the class results, $$P(t)$$ is written as: $$P(t) = \begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix} + \sum_{k=1}^{\infty} \frac{t^k}{k!} \begin{pmatrix} -1 & 1 \\ 1 & -1 \end{pmatrix}^k.$$ We know from the given results that: $$\begin{pmatrix} -1 & 1 \\ 1 & -1 \end{pmatrix}^k = 2^{k-1}(-1)^k \begin{pmatrix} -1 & 1 \\ 1 & -1 \end{pmatrix}.$$ This reduces $$P(t)$$ to an exponential form. Finally, for $$p_{11}(t)$$ (probability of being in state 1 at time $$t$$, starting at state 1): $$p_{11}(t) = P(X(t) = 1 \mid X(0) = 1).$$ --- ### **Question 2: Distribution for the Number of Moves in Time $$t$$** For the Markov process described, the number of moves follows a Poisson distribution. To derive $$p_{11}(t)$$ based on the number of moves: - If $$k$$ (even) is the number of moves, the probability of returning to state 1 is computed as: $$p_{11}(t) = \sum_{k=0, k \text{ even}}^{\infty} \frac{t^k}{k!} e^{-t}.$$ #### Verify Equality: The $$p_{11}(t)$$ from the transition matrix (part 1) and from the number of moves (part 2) must be identical. This can be verified by using: $$\sum_{k=0, k \text{ even}}^{\infty} \frac{t^k}{k!} = \frac{1}{2}(e^t + e^{-t}).$$ --- ### **Question 3: Numerical Verification** Numerical methods can confirm the equivalence between the two expressions for $$p_{11}(t)$$: 1. Compute $$P(t)$$ using matrix exponentiation. 2. Compare with the summation formula for $$p_{11}(t)$$ in terms of even $$k$$. --- Would you like detailed step-by-step calculations or a numerical example implemented? Let me know! --- ### **5 Related Questions** 1. What is the role of matrix exponentiation in continuous-time Markov processes? 2. How does the Poisson distribution model the number of transitions in a fixed time? 3. Why is the summation restricted to even $$k$$ in $$p_{11}(t)$$? 4. How does $$p_{11}(t)$$ behave as $$t \to 0$$ or $$t \to \infty$$? 5. What are practical applications of such a two-state Markov process? ### **Tip** When working with matrix exponentials, remember that simplifying the powers of matrices using properties (e.g., symmetry or idempotence) can significantly reduce computation effort.

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Math Problem Analysis

Mathematical Concepts

Continuous-time Markov processes
Matrix exponentiation
Poisson distribution
Summation of series

Formulas

P(X(t+h) = k | X(t) = j) = h if j ≠ k, and 1-h if j = k
P(t) = I + ∑ (t^k / k!) (-1)^k G^k
p_11(t) = ∑_{k=0, k even} t^k / k! * e^(-t)

Theorems

Matrix exponential representation for Markov processes
Properties of the Poisson distribution
Series summation techniques

Suitable Grade Level

Graduate level (Mathematics or Statistics)